The acceptance of a software system by its users crucially depends on the system’s ability to meet its quality requirements. In this context, the relevant quality factors as well as their importance differ between domains, between organizations, and even between development projects within an organization. The UML QoS-Profile proposes a flexible framework for modelling quality requirements with the UML. However, the QoS-Profile does not offer guidelines on how to derive relevant quality factors that can be used for modelling quality requirements with the UML. Even though reference modelling techniques (e.g. domain engineering) provide an appropriate solution if suffi-cient resources are available – they lack in scalability if this is not the case. In this position paper we sketch a scalable approach for defining QoS reference models that is based on well-established requirements engineering techniques.